This study is intended to provide new information about the effects of ischemia, drug interventions, and other factors on the regional metabolism of perfused mammalian organs including kidney, heart and brain, and on the rates of enzymatic reactions in these specific zones. High-resolution P31 NMR spectra of the zone of interest will be obtained using the sensitive point technique. In vivo reaction rates of certain kinase, ATPase and probably other enzymes will be measured both in vitro and in vivo by the method of saturation transfer. The results will be used to 1) validate these methods for enzymological and organ studies, 2) shed light on the biochemical aspects of ischemic damage to tissues and suggest procedures to minimize such damage.